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NCERT Solutions for Class 12 Biology Chapter 7 Evolution
Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
When a bacterial population encounters a particular antibiotic, those sensitive to it, die. Sometimes a bacterial population happens to contain a few bacteria having mutations which make them resistant to the antibiotic. Such resistant bacteria survive and multiply quickly. Soon the resistance providing genes become widespread and entire bacterial population becomes resistant. This type of sorting out of the organisms with useful variations has been called as ‘natural selection’ by Darwin.
Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
Chimps are more evolved than humans (The Times of India):
Chimpanzees are more evolved than humans, a study suggests. There is no doubt that humans are the more advanced species. But a comparison of 14,000 human and chimpanzee genes shows the forces of natural selection have and the greatest impact on our ape cousins.
The researchers’ discovery challenges the common assumption that our large brains and high intelligence were the gifts of natural selection. Humans and chimps followed different evolutionary paths from a common ape ancestor about 5 million years ago. Both underwent changes as the fittest survived to pass their genes on to future generations. But the US study shows that humans possess a ‘substantially smaller’ number of positively-selected genes than chimps.
Attempt giving a clear definition of the term species.
Species (used both as singular and plural) is a natural population of individuals or group of populations which resemble one another in all essential morphological and reproductive characters so that they are able to interbreed freely and produce fertile offspring.
Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
Human evolution shows the following trends :
A. Brain size : It increased gradually along with evolution. The brain capacity of Australopithecus africanus – 500 cc, Homo habilis – 700 cc, Homo eredus – 800 – 1300 cc, Homo sapiens sapiens – 1450 cc.
B. Skeletal structure:
- Dryopithecus was ape-like, without browridges, had semierect posture, and prognathous face (having a projecting jaw).
- Ramapithecus had jaws and teeth like humans (small canines and large molars), prognathous face and walked on legs
- Australopithecus africanus had erect posture, human like teeth, was without chin, with browridges, and had prognathous face.
- Homo habilis walked nearly erect, had human like teeth, with browridges face was slightly prognathous.
- Homo erectus had erect posture, prognathous face, with projecting browridges, small canines and large molar teeth and had small chin.
- Homo sapiens sapiens had four curves in the vertebral column, orthognathous face (without projecting jaw), forehead broad, chin well developed, walked on sole.
C. Dietary preference: Dryopithecus and Ram-apithecus were herbivores, Australopithecus africanus and Homo habilis were carnivores, Homo erectus and Homo sapiens sapiens were omnivores.
Find out through internet and popular science articles whether animals other than man have self-consciousness.
Yes, chimpanzees are most near to the man than any other living animal and have self-consciousness.
List 5-6 modern day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
List of few modern day animals and their corresponding ancient fossils is as follows:
Describe one example of adaptive radiation.
The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation. Adaptive radiation gave rise to Australian marsupials. A number of marsupials, each different from the other evolved from an ancestral stock, but all within the Australian island continent.
Can we call human evolution as adaptive radiation?
No, we cannot call human evolution as adaptive radiation
Using various resources such as your school library or the Internet and discussions with your teacher, trace the evolutionary stages of any one animal say horse.
The evolutionary stages of modern horse are listed in the table given below:
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